CA1249659A - Optical disc having servo-track portions and sector addresses and apparatus - Google Patents
Optical disc having servo-track portions and sector addresses and apparatusInfo
- Publication number
- CA1249659A CA1249659A CA000499736A CA499736A CA1249659A CA 1249659 A CA1249659 A CA 1249659A CA 000499736 A CA000499736 A CA 000499736A CA 499736 A CA499736 A CA 499736A CA 1249659 A CA1249659 A CA 1249659A
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- Prior art keywords
- servo
- track
- record
- radiation
- carrier body
- Prior art date
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- Expired
Links
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- 230000005855 radiation Effects 0.000 claims description 77
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- 238000004519 manufacturing process Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000011896 sensitive detection Methods 0.000 description 2
- 241001527902 Aratus Species 0.000 description 1
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- 239000000463 material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000002674 ointment Substances 0.000 description 1
- 239000011253 protective coating Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
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Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/26—Apparatus or processes specially adapted for the manufacture of record carriers
- G11B7/261—Preparing a master, e.g. exposing photoresist, electroforming
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B23/00—Record carriers not specific to the method of recording or reproducing; Accessories, e.g. containers, specially adapted for co-operation with the recording or reproducing apparatus ; Intermediate mediums; Apparatus or processes specially adapted for their manufacture
- G11B23/0057—Intermediate mediums, i.e. mediums provided with an information structure not specific to the method of reproducing or duplication such as matrixes for mechanical pressing of an information structure ; record carriers having a relief information structure provided with or included in layers not specific for a single reproducing method; apparatus or processes specially adapted for their manufacture
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/007—Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/007—Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track
- G11B7/00745—Sectoring or header formats within a track
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0938—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following servo format, e.g. guide tracks, pilot signals
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/2407—Tracks or pits; Shape, structure or physical properties thereof
- G11B7/24073—Tracks
- G11B7/24079—Width or depth
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Optical Recording Or Reproduction (AREA)
- Optical Record Carriers And Manufacture Thereof (AREA)
Abstract
ABSTRACT:
Record-carrier body provided with a relief structure of optically detectable servo-track portions and sector addresess and apparatus for forming said structure.
A record carrier body is describe provided with sector addresses (12) and servo-track portions (13). As the maximum width of the servo-track portions is at least 60% of the track period (Pr), in a direction transverse to the track direction, and is at least of the order of twice the maximum width of the sector-address areas (15), it is possible to obtain an improved tracking signal in addition to a satisfactory address signal. An improved information signal can be obtained by recording the information (22) in the lands between the servo tracks.
Fig. 7.
Record-carrier body provided with a relief structure of optically detectable servo-track portions and sector addresess and apparatus for forming said structure.
A record carrier body is describe provided with sector addresses (12) and servo-track portions (13). As the maximum width of the servo-track portions is at least 60% of the track period (Pr), in a direction transverse to the track direction, and is at least of the order of twice the maximum width of the sector-address areas (15), it is possible to obtain an improved tracking signal in addition to a satisfactory address signal. An improved information signal can be obtained by recording the information (22) in the lands between the servo tracks.
Fig. 7.
Description
lZ4~659 PHN 11.261 1 20.6.1985 Record-carrier body provided with a relief structure of optically detectable servo-track portion~ and sector addresses and apparatus for forming said structure.
The invention relates to a record-carrier body in which a user can record information by means of optical radiation~ which record-carrier body comprises a substrate and a recording layer on said substrate and which has been provided with a preformed optically detectable relief structure of servo-track portions and ~ector addresses in which address information about associated recordable portions of the record-carrier body is contained in the form of optically detectable areas which alternate with 10 intermediate areas~ which areas in the sector addresses have another phase depth than the servo-track portions. The invention also relates to an apparatus for recording a structure in conformity with the relief structure of sector addres~es and servo-track portions of said record-carrier 15 body.
The record-carrier body may be a circular disc-shaped substrate carrying a recording layer in which optically detectable changes can be produced by a radiation beam of sufficiently high intensity. The servo-track 20 portions may comprise grooves recessed in the substrate surface or ridges formed on the substrate surface, and the sector-address areas may comprise pits recessed in the substrate surface or hills formed on this surface. The sector addresses may be situated het~ree~ successive s~rvo 25 track portions, viewed in the track direction, so as to form one composite track. Thi~ track extends over the entire surface area of the recording layer and is preferably a spiral track, but alternatively it may comprise a multitude of concentric tracks.
When the sector addresseY and servo track portions are exposed to a radiation beam which is focussed to form a small radiation spot~ this beam is split into a zero-order , ~
i2~659 PHN 11.261 2 20.6.1985 subbeam, fir~t-order subbeams and higher-order subbeams.
Herein, phase depth is to be understood to mean the phase difference between ths ~ero-order subbeam and a first-order subbeam. This phase depth i8 deteI~ined by the geometry of the sector-address areas and the servo-track portlons~ inter alia by the depth or height of these areas and track portions.
Such a record-carrier body i9 known inter alia from United States Patent Specification No. 4,363,t16.
As de9cribed in said Patent Specification, the servo-track portions are employed during the recording of information by the user for detecting and correcting the radial position of a radiation spot formed on the recording layer by a radiation beam. This enables the requirements imposed on the drive and guide mechanisms, for moving the write spot and the record carrier body relative to each other~
to be less stringent~ so that the write apparatus can be simpler and cheaper.
Preferably~ the radial position of the radiation spot relative to a servo-track portion is detected by means of the "pu~h-pull" or differential method. This method employs two radiation-sensitive detectors~ which are arranged in the path of the radiation beam i~suing from the record carrier body and which receive radially diffe-rent portions of this beam. The difference between theoutput signals of the two detectors contains information about the radial position of the radiation spot relative to the servo-track portion. If said output signals are equal, the centre of the radiation spot coincides with the central axis of the servo-track portion. The diffe-rential tracking method may be employed only if the servo grooves have such a depth or the servo ridges have such a height that their phase depth is of the order of 90.
The sector-address areas are read using the "Central-Aperture" or integral method. In accordance with this method the variation of the overall intensity of the radiation originating from the record carrier body lZ4~659 and traversing an objective system is detected by means of a single detector arranqed on the optical axis or by means of the two detectors employed for tracking, whose output signals are added to each other. For optimum read-out of the sector addresses the areas therein should have a phase depth of approximately 180.
It has been found that, in addition to the phase depth, the width, measured in the direction transverse to the track direction, of the servo- track portions and the 10 sector-address areas also has a substantial influence on the amplitude of the signals obtained when the user information is recorded. In the record-carrier body in accordance with United States Patent Specification no.
4,363,116, which is intended to be scanned by means of a 15 radiatian spot whose half-intensity value is approximately 800 nm, the servo-track portions and the sector-address areas have a width of approximately 600 nm, whilst the period, transverse to the track direction, of the track structure is approximately 1600 nm. The half-intensity 20 diameter of a radiation spit is equal to the distance between two points where the intensity is half the inten-sity in the centre of the radiation spot. By means of the kncwn record-carrier body it is possible to obtain a different tracking signal of moderate signal amplitude.
2s It is an object of the invention to provide a record-carrier body which, when scanned for the purpose of informatian recording, produces a differential tracking signal of substantially higher signal amplitude. It is anDther object of the invention to obtain an improved 30 information si~nal of higher siqnal amplitude when the information areas recorded by the user are read in accor-dance with the inteqral read m~thod.
In accordance with a first aspect of the inven-tian the record-carrier body is characterized in that the 35 maximun width of the servc~track portions is at least 60 ~ of the track period, transverse to the track direction, . . .
iZ~9659 PHN. 11 261 4 and is at least of the order of twice the maximum width of the sector-address areas.
The use of the concept "maximum width" is related to the fact that the servo grooves or ridges and the sector-address pits or hills need not have perpendicular walls, but in practice generally have oblique walls. The maximum width is then the width at the location of the recording-layer surface which is remote from the substrate.
Apart from a maximum width the servo grooves and sector-address pits also have an effective width. The shallow servo grooves are generally V-shaped in cross-section. For such a groove shape the geometrical effective width is approximately half the maximum width. The deeper pits in the sector addresses are frequently trapezoidal. For such pits the effective width is equal to half the sum of the maximum width and the minimum width.
The invention is based on the recognition of the fact that for a maximum amplitude of the differential tracking signal the effective width of the servo-track portions should be of the order of half the track period, whilst for a maximum amplitude of the integral read signal produced by the sector address areas the effective width of these areas should be of the order of one third of the track period. In accordance with the invention the concept used until now in the manufacture of the master disc for such record-carrier bodies, of recording both sector addresses and the servo-track portions by means of one radiation spot, is abandoned and two radiation spots of different dimensions are used, so that the sector address areas and the servo-track portions each can be given their optimum widths, which differ from each other.
It is to be noted that U.S. Patent 4,587,648 describes a record-carrier body provided with servo-track portions in the form of grooves and sector addresses in the form of pits. In said Patent Application it is stated that the width of the servo grooves may be equal to or larger than the width of the pits in the sector addresses. However, said European Patent Application deals with the problem that at 124~6;59 PHN. 11 261 5 the location of the sector address a satisfactory tracking by means of differential method is not possible if the pits of the sector addresses have a depth of ~/4, which corresponds to a phase depth of 18~ for pits having straight walls.
Here, ~is the wavelength of the radiation beam used for reading the addresses and recording the user information. In order to solve this problem it is proposed to give the pits of the sector addresses the same depth as the servo grooves, i.e. the depth of the order of an odd multiple of ~/8, which corresponds to a phase depth of approximately 90 for pits having straight walls. In this record-carrier body the phase depths of the pits and the grooves therefore are not different as in the record carrier body in accordance with the present invention. Moreover, and which is even more important, the ratio between the widths of the servo-track portions and the sector-address areas in the record carrier body in accordance with European Patent Application No.
0,100,995 differs from that in the record-carrier body proposed in the present Application.
In said U.S. Patent 4,587,648 the widths are expressed as the half-intensity width W0 of the scanning spot. The servo grooves have a width of Wo/2 and the pits of the sector addresses have a width of Wo/3, so that the width of the servo grooves is approximately 1.5 times the width of the pits. In a record carier body in accordance with a preferred embodiment of the invention, which is intended to be scanned by means of a radiation spot whose half-intensity width is approximately 800 nm, the width of the servo-track portions is approximatelky 1200 nm, or 3/2.W~, and that of the pits is approximately 600 nm, or 3/4.W~. Further, European Patent Application No. 0,100,995 does not mention anything about the relation between the maximum track width and the track period.
In accordance with a second aspect of the invention ~24!~6S9 PHN 11.261 6 20.6.1985 two radiation spot 9 ~ for recording the servo-track area~ and the sector addresses respectively~ are utilized in order to increase the amplitude of the ~ignal obtained during the subsequent read-out of the information recorded by the user. In accordance with this aspect a record carrier in accordance with the inventiDn i~ characterized in that the servo-track portions constitute continuous tracks and the sector addresses are situated between servo tracks which are ~ituated ad~acent each other in a direc-tion transverse to the track direction.
In this record carrier body a user does not recordthe information in the servo-track portions, as was custo-mary until now, but in the lands between the servo tracks, i.e. on flat parts of the recording lay~r. As a result of this~ the information areas, which comprice mel-ted-away portions of the recording layer, can be detected better than when the~e areas are situated in the servo grooves.
The invention further relates to apparatus for forming a structure of sector addresses and servo-track areas on a photo-sensitive layer of a master disc. This apparatus, which comprises a radiation-source system for producing two radiation beams, a separate intensity modula-tor for each of the beams, and an objective system for focussing the beams to form two radiation spots of different dimensions, is characterized in that the smaller radiation spot is employed for recording the sector addresses and the larger radiation spot for recording the servo-track portions.
It is to be noted that it is known from United States Patent Specification no. 4~027,330 to employ two radiation spots for simultaneously recording information areas and a servo track. In accordance with this United States Patent Specification, however, the wider radiation spot is employed for recording broader information areas and the narrower radiation spot for recording a narrow ~ervo track. The information areas have the form of locally wide-ned portions of the qervo track and are distributed over the lZ ~659 PHN 11,261 7 20.6.1985 entire length of the servo track and hence do not constitute ~ector-address areas.
The apparatuR in accordance with the invention may be characterized further in that, viewed in a direction tran~ver~e to the longitudinal direction ofthe servo-track portions to be recorded, the two radiation spot~
have the same position.
However, preferably, the apparatu~ i~ characterzed further in that, viewed in a direction transverse to the longitudinal direction of the ~ervo-track portions to be recorded, the two radiation ~pots are shifted relative to one another.
The sector addresses are then recorded between the turns of the servo track. The user information is subse-quently also recorded in these lands~ which enables theinformation areas to be read more effectively by means of the integral read method.
For reading the sector addresses and recording information in a record carrier body having continous servo tracks and sector addresses situated between these tracks, a user mu~t employ a write-read apparatus modified in accordance with the invention, This apparatus, which comprises a radiation-~ource system for producing a single or double write-read beam, an inten~ity modulator arranged in the path of the beam, and an objective system for focussing the beam to form a single or double write/
read spot, is characterized in that there is provided an auxiliary beam for the purpose of tracking, which auxiliary beam is focused by mean~ of the ob~ective system to form an auxiliary radiation spot which, viewed in a direction transver~e to the direction of a servo track, is shifted relative to the single or doublewrite/read spot over the distance equal to half the track period in a direction transverseto the track direction.
After the user ha~ recorded information in the record-carrier body in accordance with the preferred embodiment, a record carrier is obtained which is 12~659 PHN 11.261 8 20.6.1985 characterized by continaus ~ervo tracks between which sector addresses are situated, information areas being recorded between successive sector addresses, viewed in the track direction.
Embodiments of the inYention will now be described in more detail~ by way of example~ with reference to the accompanying drawings. In the drawings :
Fig. 1 is a plan view of a part of a record carrier body in accordance with a first embodiment of the invention, Fig. 2 shows two ad~acent sector addresses of this record carrier body to an enlarged scale, Fig. 3 is a radial sectional view of a part of said record carrier body at a location outside the sector lS addresses, Fig. 4 is a radial sectional view of a part of said record carrier body at the location of the sector addresses, Fig 5 is a tangential sectional view of a part of 9aid record carrier body, Fig~ 6 is a plan view of a part of a record carrier body in accordance with a preferred embodiment of the invention, Fig. 7 is a radial sectional view of a part of said record carrierbody at the location of sector addres~es, Fig. 8 is a tangential sectional view of a part of said record carrier body, Figure 9 shows an apparatus for recording the sector addresses and the servo-track portions, in accordance with a fir~t embodiment of the invention, Fig. 10 shows a part of such an apparatus in accordance with a second embodiment, and Fig. 11 shows a combined write/read apparatus for recording and reading information in a record-carrier body in accordance with the invention.
The record-carrier body 1 as shown in Figure 1 comprises a track 10, for example a spiral track~ of which ~2~6~9 PHN 11.261 9 20.6.19~5 Figure 1 ghows only two of the multitude of turns.
Each turn of the track is divided into a large number of sectors~ for e~ample 64 of 128. Each sector comprise~ a servo-track portion 13~ in which a user can record information, and a sector address 12~ in which inter alia the address of the associated 3ervo-track portion 13 is encoded in digital form in optically readable areas 15 shown in Figure Z. Both these area~ and the servo--track portions 13 can be detected optically, 90 that before a block of information is recorded the desired addres~
can be detected and, both before and during recording, steps can be taken to ensure that a write spot accurately follows the servo-track portions. The record-carrier body 1 has a recording layer in which an optically detectable change isproduced when it is expo2led to radiation of sufficiently high intensity.
The method by which and the a E~aratus by means of which the addresses are read and the servo track portions are followed during the recording of the information by the user and the manner in which the recorded user information can be read fall beyond the scope of the present invention and are therefore not described here.
For these subjects reference is made to United States Patent Specification no. 4,363,116.
Figure 2 shows part of two radially adjacent sectors of the track 10. As is shown in this Figure, the sector addres~es are formed by areas 15 which alternate with intermediate areas 16 in the track direc-tion. Between the consecutive turns of the track 10 lands 14 are situated at the same level as the intermediate areas 16. The servo track portions may comprise ridges situated on the surface of the intermediate areas 16 and the lands 14 or, as is shown in Figure 3, grooves recesYed in this surface. In the latter case the sector addres~ areas comprise pits in said surface, which are deeper than the servo grooves, as can be seen in Figure 4.
It is to be noted that for the sake of clarity the iZ4~ 59 widths of the track 10 and of the lands 14 in Figlre 1 have been exaggerated in conparison with the total surface areas of the record carrier. In reality the record carrier body has a diameter of, for example, approximately 30 cm and the radial period Pr~ i.e. the period of the track structure in the radial direction r, is, for example, 1600 nm. The length of the sec~or addresses has also been exaggerated in comparison with the servo track portions 13. In practioe , the length of the portions 13 is, for example of the order 10 of magnitude of 10 to 100 times the length of the sector addresses 12.
Figure 3 is a radial sectional view of a part of the record carrier ~ody, taken on the line 3-3' in Figure 1, at a location where only servo~track portions 13 are situated. The servo-track portions 13 comprise grooves 15 recessed in the surfaces of the lands 14, which grooves can be followed by means of the differential method.
As set forth in British Patent Specification no. 2,034,097 these grooves have a phase depth of the order of 90.
These grooves are shallow and their walls have a large 20 angle of inclination e1, of the order of 80. The substrate 17 carries a thin recording layer 18. This layer may be a reflecting layer, comprisinq, for example, bismuth or tellurium as its principal element. The track structure is then scanned with a beam which is projected from underneath 25 and which traverses the substrate, as is indicated by the arrow 19. Moreover, a protective coating 20 may be provided on the recording layer 18.
Figure 4 is a radial sectional view taken on the line 4-4' in Figure 1, showing a part of the reoord-30 carrier body at the location where the sector addressesare situated. It has been assumed that at the location where the sectional view has been taken two areas 15 are situated adjacent each other in the radial direction.
As will become apparent from a comparison with Figure 3, 35 these areas are deeper than the ser~ trackportions, whilst the angle of inclination ~2 is, for example, of the order of 30 to 60.
,,, i2~9659 Fig. 5 is a tangential sectional view of a part of the record-carrier bcdy, taken on the line 5-5' in Figure 1. As Figure 5 shcws, each sector address comprises an address portion 12a an~ a synchronizing portion 12b, which each comprise a plurality of pits 15 of uniform dimensions, recessed in the substrate. The sequence of pits in the por ion 12a represents the a~dress information.
The pits in the portion 12b have a fixed spatial frequency and upon read-out they produce a clock siqnal for 10 controlling, for example, the clock frequency of a signal source which serves for modulating the amplitude of the write beam with which the user records the information.
By means of a write beam whose intensity is modulated in conformity with the user information to be recorded, for 15 example, pits 22 can be melted in the recording layer at the location of the track portions 13, so that information areas are formed which have a different reflection coe fficient than the surrcunding areas. After the information has been recorded the user has a record carrier in which the servo-20 track portions 13 and the sector addresses 12 constitute aphase structure, whilst the user information has been recorded in the form of, for example, an amplitude structure.
In accordance with the invention, as will be apparent fram Fig~re 1 and a comparison of Figures 3 and 4, 25 the maximum width Wmax 1 of the servo track portions is at least twice the maximum wldth Wmax 2 of the sector-address areas and WmaX1 is larger than half the track period in the radial direction (Pr). In a record carrier for which Pr =
1600 nm and which is intended to be scanned with a 30 radiation spot whose half-intensity value is approximately 800nm, Wmax 1 is approximately 1200 nm and Wmax 2 is approximately 600 nm. The larger width of the servo~track portions ensures that the differential tracking signal has a better signal amplitude than the tracking si~nal 35 obkained from record-carrier bodies Xncwn until ncw, in which the maximum track width is equal to the maximum width of the sector address areas and is, for example, 600 nm.
i24~659 An important advantage is, moreover, that for the specified width of the servo track portions 13 the informa-tion æeas 22 recorded in these portions ky the user can ke read ~etter by means of the integral method than such track s portions 13 having a smaller width. The last-mentioned effect can be explained from the fact that the information areas 22, which differ from their surrounding æea in that they have a different coefficient of reflection, can be detected better when the groove portions 13 æe wider and 10 kear greater resemblance to the flat portions of the recording layer.
The optim~m value of the maximum track width for differential tracking and for integral reading from the sector-address areas provided ky the invention, is the 15 result of inventive use of insights oktained ky vectorial diffraction co~putations. These show that as the servor track portion kecomes wider the amplitudes of the second and higher even diffraction orders decrease and, if the track depth rem2ins the same, the ~.~litude of a first-order suk 20 keam increases as a result of the larger volume of the servo groove or ridge, and that as the maximum track width more closely approximates to the radial period of the track structure the phase depth will come closer to the optimum value of 90, even for larger depths of the servo track.
2s It has keen found that a specific value for the maxim~m track width can ke specified above which the amplitude of the differential tracking signal h ædly increases. For a record carrier kody which has a period Pr f the order of 1600 nm and which is scanned with a radiation spot whose 30 half-intensity value is approximately 800 nm, said value is approximately 1200 nm.
The vectorial diffraction theory teaches that the differential tracking signal is ideal for an effective track width e~ual to approximately half the radial track period.
35 For V-shaped servo grooves this means that the maximum groove width is sukstantially equal to the track period, so that the grooves would adjoin each other. From the point of view of manufacturing technology this is i2~ ;5g PHN 11.261 13 20.6.1985 undesirable. However~ it is also found that for de~iations of the order of 25~ from the ideal track width a ~ery acceptable tracking signal can be obtained.
Therefore~ for practical versions of the record carrier body in accordance with the invention the optimum value for the maximum width of the servo-track portions i9 of the order of 75~ of the radial track period~ Deviations of the order of 20~ from this optimum value are permissible.
Figure 6 shows a record carrier body in accordance with a preferred embodiment of the invention. In this embodiment the servo-track portions ad~oin each other in a tangent~l direction and constitute a continous spiral track or continuous concentric tracks 13. The sector addresses are now situated between the turn~ of the servo track 13.
The optimum value for the maximum width of the servo track 13 is again of the order of 7g~ of the radial period Pr, and the maximum track width is again at least twice the maximum width of the sector-address areas.
Figure 7 is a radial sectional view of a part of this record-carrier body~ taken on the line 7-7' in Figure 6 at the location where the sector addresses are situated.
It is assumed that at the location where this sectional view is taken two areas 15 ad~oin each other in a radial direction. After the description of the first embodiment with reference to the Figures 3 and 4~ Fig. 7 is self-explanatory. Figure 8 is a tangential sectional view of a part of the record-carrier body, taken on the line 8-8' in Figure 6. This Figure also requires no further 3~ explanation.
In the record-carrier body shown in Figure 6 the information areas 22 are recorded by the user ~n the lands between two ~ero-track portions 13 and between two ~ector addresse~ 12. Since the surface for recording the information areas is now entirely flat~ these areas can be read even better by means of the integral method than in the case where the informatiQn areas are recorded in lZ~3659 the wide servo track portions of the record carrier body 1 shown in Figure 1, It is to be noted that the recording of the user-information between the servD grooves or ridges need not be combined with a wider servo groove, but may also be applied to a record-carrier body with a narrcwer servo groove. Recording the information areas between the servo grooves or ridges then also has the advantage that these areas can be read more effectively.
Figure 9 shows the basic diagram of an apparatus by means of which the sector addresses and the servo-track portions on a master disc can be produced. In this Figure the reference numeral 30 denotes the substrate of the master disc, for example a glass substrate. This substrate carries a photo-15 sensitive layer 31, whose thickness has been selected in such a way that the sector-aadress areas, formed after the development of the photo-sensitive layer, have a depth or height which is adapted to the wavelenqth of the beam with which the record-carrier body is to be scanned in order 20 to obtain the correct phase depth. A radiation-source system 33 may comprise one laser or two separate lasers 34 and 35, for example ægon-ion lasers. This system produces tw~ radiation beams bl and b2, of which b1 serves for re-cording the sector addresses and b2 for recording the servc-25 track portions. The narrow beams are widened, for exampleby means of telesco~es comprising lenses 36, 37 and 39, 40 respectively, the beam bl being wiAened more than the beam b2.
Thus, the beam bl is given such a width that it fills a substantial part of the entrance pupil of the objective 30 systems 45. After havin~ traversed its telescope the beam b2 is coupled into the path of the beam bl by the mirror 42 and a beam splitter, for example in the form of a beam-splitting mirror 43. A mirror 44 reflects the two beams to the objective system 45, which focusses each of the beams to 35 form radiation spits V1 and V2, respectively. Since the beam blfills a substantial part of the pupil of the objective system, this beam is focussed to a minimal diffraction-iZ4~659 limited radiation spot. The beam b2, which fills a small part of the pupil, is focussed to form a 'arger radiation spot V2.
By rotating the disc about the axis 32 the radiation s spots V1 and V2 will describe one turn on the disc. For recording a spiral track or a plurality of concentric tracks the radiation spots and the disc should be moved in a radial direction relative to each other either with a constant velocity or stepwise. For this purpose, the mirror 10 44 and the objective system 45 may be accommodated in a housing which is moved in the direction inaicated by the arrow 46.
Mbdulators 47 and 49, for example acousto-optical modulators, are arranged in the radiation paths of the beam 15 b1and the beam b2, respectively, to switch the intensity of the relevant beam in conformity with the signal applied to the terminals 48, 48' and 50, 50', respectively. When the sector addresses are recorded the modulator 47 is switched between a high level and a zero level at a high 20 frequency. In the present apparatus the modulator 49 is then set to the zero level. Durin~ the recording of the servo-track portions the modulator 47 is set to the zero level and the modulator 49 cperates continuously at an intermediate level.
2s The exposure locally increases the solubility of the photo-sensitive layer. The desired relief pattern is obtained by a selective removal of the exposed photo-sensitive material in a development process. The depth and the width of the servo groove are determined by the 30 intensity of the beam b2 and the width of the radiation spot V2, respectively. After the master disc has been developed it may be coated with, for example, a silver layer.
Subsequently, this disc may be used in known manner for the manufactNre of matrices, which are employed for the 35 manufacture of a large number of replicas.
If the chief rays of the beams b1 and b2 are situated in the same X-Y plane, the radiation spots Vl and V2 are superimposed, as sho~n in the inset in the right-~z~s~
PHN 11.261 16 ZO.6.1985 hand part of Figure 9, assuming that the mirrors42 and 43 aro disposed at angles of 45 to said chief rays. Alternatively~ the radiation spots may be shifted in the tangential direction of the disc, i.e. in the Y-direction in Figure 9, in such a way that the radiation spot V1 i9 situated in front. For this purpose the radiation paths of the beams b1 and b2 should be shifted slightly relative to each other in the Y-direction.
For recording continous servo tracks and sector addresses between the turns of the servo tracks it is in principle possible to use an arrangement sim~lar to that shown in Figure 9, in which the modulator 49 is always at the intermediate level and the modulator 47 i9 switched between the high level and the zero level with a high frequency when the sector addresses are being recorded.
The radial shift of the radiation spots V1 and V2 relative to each other can be obtained, for example, by positioning the mirror 42 at an angle which differs slightly from 45 relative to the chief ray of the beam b2, as is shown in Figure 10. This Figure shows only that part of the radiation path where the beams are given different directions, i.e. the part beginning at the mirror 42.
Figures 9 and 10 show the basic diagram of the apparatus for recording the sector addresses and the servo-track portions, in which apparatus a number of variants are possible. For example, the radiation-source system may comprise only one laser followed by a beam splitter. In order to minimize the 109s of intensity this beam splitter and the beam splitter 43 are preferably polarisation-dependent beam splitters and the single radiation source, or the double radiation source 34~ 35, should be capable of producing two beams which are polarised perpendicularily to each other. It is also possible to employ wavelength-selective beam splitters in con~unction with a single ordouble radiation source, emitting two different wavelengths.
A shift of the radiation spots V1 and V2 in a radial direction~ the X-direction in Figure 9~ can also be 12'~!-3659 obtained ky an optical wedge in the p~th of the beam b2, the mirror 42 extending parallel to the beam-splitting mirror 43.
The user of the record-carrier body should have a ccmbined recording/read apparatus at his disposal for recor-ding information and reading this information, and for reading the sector addresses both during recording and during infor-mation reading. Such combined apparatus are known, for example fram United States Patent Spscification no. 4,363,116 and 10 British Patent Specification no. 2,097,150. The known app æatus æe suitable for use in conjunction with a record-c ærier kody in which the sector addresses occupv the same radial positions as the associated serv~-track portions. For a record-carrier body in which the servo~track portions constitute continuous tracks lS and the sector addresses æ e situated between the turns of the servo track, the tracking systemin the known write/read apparatus may be mcdified in such a way that the scanning spot is held at a constant distance from the serv~ track in a way similæ to that described in British Patent Specification 20 2,013,489 for a record carrier with deep and shallcw tracks.
Another possibility is to provide the known write/read apparatus with means for the formation of an additional radiation spot for the purpose of tracking.
Figure 11 shows an example of such an appæ atus. This 2s Figure only shcws the elements of the tracking system. The ele-ment 60 is a radiation source, for example a diode laser, which produces a beam b3. The lenses 61 and 62 constitute a beamr widening telescope which ensures that the beam b3 fills the pupil of theobjective system 67 correctly. Instead of the telescope a 30 lens may be used, which is æranged between the mirror 65 and the objective system 67. The beam reaches this objective system after reflections from the mirror 63, the beamrsplitting mirror 64 and the mirror 65. The objective systemfocusses the beam b3 to form a diffraction-limited radiation spot V3 on the recording layer 18 35 of the record-cærier body 1. This body can be rotated abcut an axis 68, and the mirror 65 and the objective system 67 can be moved together in a radial direction relative to the record-carrier bo~y, the X-direction in Fig~re 11, as indicated by the mirror 75.
124~6S~
The mirror 63 and the beam-splitting mirror 65 serve to couple the auxiliary beam b3 into the mainradiation path of the apparatus, so that all the beams pass through the same ob-jective system. me main radiation path is represented schema-5 tically by a broiad bea~ bo 1 (bo 2) indicated by double arrcws.The block 69 together with the mirror 65 and the objective system 67 constitute the known part of the apparatus. As is descriked in United States Patent Specification no. 4,363,116, it is possible to use only one radiation spot koth for recording and reading.
10 In that case the block 69 co~prises one radiation source, for example a diode laser, a beam~widening and collimating lens system, a modulator, a radiation-sensitive detection syste, and a beam splitter for diverting the radiation which has bPen re-flected by the record carrier body to the detection system which 15 supplies the address signals and the information signals.
Another version of the block 69 produces two radiation beams bo 1 and bo 2 which are focussed by the objective system to form two radiation spots V1 and V2 which are shifted relative to each other in the tangential 20 direction of the record-carrier body, i.e. in the Y-direction in Figure 11. The radiation spots v1, V2 and V3 have the same dimensions. In the present example the block 69 comprises, for example, two diode lasers, a beam splitter for re~ombining the two laser beams after o,ne of 25 them has passed through a modulator, a second beam splitter for diverting the beams reflected by the record-carrier body, a third beam splitter fo,r separating the two beams, and a separate detection system for each of the beams. The beam bo 1~ which forms the radiation spot V1, serves 30 for reading the clock signals and the addresses and for recording the information, and the beam bo 2' which forms the radiation spot V2, is employed fo,r reading the information. For further details about a block 69 which is capable of producing one or two radiation beams reference 35 is made to the United States Patent Specification no.
4,363,116 and British Patent Specification no. 2,097,150, respectively.
i2~96S9 The auxiliary beam b3 is reflected ~y the record-c ærier body and returns along itself until it reaches a beam splitter 70. This beam splitter reflects a part of the beam b3 to a radiation-sensitive detection system ccmprising 5 tw~ detectors 71 and 72. The output signals of these detectors æe applied to a differential amplifier 73. The output signal Sr of this amplifier contains information about the magnitude and the direction of a deviation between the centre of the radiation spot V3 and the 10 central axis of the serv~ track. This signal is employed for correcting the radial position of the radiation spot V3 and those of the radiation spots V1 and V2, for example by piv~ting the mirror 65 in the direction indicated by the arrow 66 by means of an actuator 74 to which the 15 signal Sr is applied.
3~
The invention relates to a record-carrier body in which a user can record information by means of optical radiation~ which record-carrier body comprises a substrate and a recording layer on said substrate and which has been provided with a preformed optically detectable relief structure of servo-track portions and ~ector addresses in which address information about associated recordable portions of the record-carrier body is contained in the form of optically detectable areas which alternate with 10 intermediate areas~ which areas in the sector addresses have another phase depth than the servo-track portions. The invention also relates to an apparatus for recording a structure in conformity with the relief structure of sector addres~es and servo-track portions of said record-carrier 15 body.
The record-carrier body may be a circular disc-shaped substrate carrying a recording layer in which optically detectable changes can be produced by a radiation beam of sufficiently high intensity. The servo-track 20 portions may comprise grooves recessed in the substrate surface or ridges formed on the substrate surface, and the sector-address areas may comprise pits recessed in the substrate surface or hills formed on this surface. The sector addresses may be situated het~ree~ successive s~rvo 25 track portions, viewed in the track direction, so as to form one composite track. Thi~ track extends over the entire surface area of the recording layer and is preferably a spiral track, but alternatively it may comprise a multitude of concentric tracks.
When the sector addresseY and servo track portions are exposed to a radiation beam which is focussed to form a small radiation spot~ this beam is split into a zero-order , ~
i2~659 PHN 11.261 2 20.6.1985 subbeam, fir~t-order subbeams and higher-order subbeams.
Herein, phase depth is to be understood to mean the phase difference between ths ~ero-order subbeam and a first-order subbeam. This phase depth i8 deteI~ined by the geometry of the sector-address areas and the servo-track portlons~ inter alia by the depth or height of these areas and track portions.
Such a record-carrier body i9 known inter alia from United States Patent Specification No. 4,363,t16.
As de9cribed in said Patent Specification, the servo-track portions are employed during the recording of information by the user for detecting and correcting the radial position of a radiation spot formed on the recording layer by a radiation beam. This enables the requirements imposed on the drive and guide mechanisms, for moving the write spot and the record carrier body relative to each other~
to be less stringent~ so that the write apparatus can be simpler and cheaper.
Preferably~ the radial position of the radiation spot relative to a servo-track portion is detected by means of the "pu~h-pull" or differential method. This method employs two radiation-sensitive detectors~ which are arranged in the path of the radiation beam i~suing from the record carrier body and which receive radially diffe-rent portions of this beam. The difference between theoutput signals of the two detectors contains information about the radial position of the radiation spot relative to the servo-track portion. If said output signals are equal, the centre of the radiation spot coincides with the central axis of the servo-track portion. The diffe-rential tracking method may be employed only if the servo grooves have such a depth or the servo ridges have such a height that their phase depth is of the order of 90.
The sector-address areas are read using the "Central-Aperture" or integral method. In accordance with this method the variation of the overall intensity of the radiation originating from the record carrier body lZ4~659 and traversing an objective system is detected by means of a single detector arranqed on the optical axis or by means of the two detectors employed for tracking, whose output signals are added to each other. For optimum read-out of the sector addresses the areas therein should have a phase depth of approximately 180.
It has been found that, in addition to the phase depth, the width, measured in the direction transverse to the track direction, of the servo- track portions and the 10 sector-address areas also has a substantial influence on the amplitude of the signals obtained when the user information is recorded. In the record-carrier body in accordance with United States Patent Specification no.
4,363,116, which is intended to be scanned by means of a 15 radiatian spot whose half-intensity value is approximately 800 nm, the servo-track portions and the sector-address areas have a width of approximately 600 nm, whilst the period, transverse to the track direction, of the track structure is approximately 1600 nm. The half-intensity 20 diameter of a radiation spit is equal to the distance between two points where the intensity is half the inten-sity in the centre of the radiation spot. By means of the kncwn record-carrier body it is possible to obtain a different tracking signal of moderate signal amplitude.
2s It is an object of the invention to provide a record-carrier body which, when scanned for the purpose of informatian recording, produces a differential tracking signal of substantially higher signal amplitude. It is anDther object of the invention to obtain an improved 30 information si~nal of higher siqnal amplitude when the information areas recorded by the user are read in accor-dance with the inteqral read m~thod.
In accordance with a first aspect of the inven-tian the record-carrier body is characterized in that the 35 maximun width of the servc~track portions is at least 60 ~ of the track period, transverse to the track direction, . . .
iZ~9659 PHN. 11 261 4 and is at least of the order of twice the maximum width of the sector-address areas.
The use of the concept "maximum width" is related to the fact that the servo grooves or ridges and the sector-address pits or hills need not have perpendicular walls, but in practice generally have oblique walls. The maximum width is then the width at the location of the recording-layer surface which is remote from the substrate.
Apart from a maximum width the servo grooves and sector-address pits also have an effective width. The shallow servo grooves are generally V-shaped in cross-section. For such a groove shape the geometrical effective width is approximately half the maximum width. The deeper pits in the sector addresses are frequently trapezoidal. For such pits the effective width is equal to half the sum of the maximum width and the minimum width.
The invention is based on the recognition of the fact that for a maximum amplitude of the differential tracking signal the effective width of the servo-track portions should be of the order of half the track period, whilst for a maximum amplitude of the integral read signal produced by the sector address areas the effective width of these areas should be of the order of one third of the track period. In accordance with the invention the concept used until now in the manufacture of the master disc for such record-carrier bodies, of recording both sector addresses and the servo-track portions by means of one radiation spot, is abandoned and two radiation spots of different dimensions are used, so that the sector address areas and the servo-track portions each can be given their optimum widths, which differ from each other.
It is to be noted that U.S. Patent 4,587,648 describes a record-carrier body provided with servo-track portions in the form of grooves and sector addresses in the form of pits. In said Patent Application it is stated that the width of the servo grooves may be equal to or larger than the width of the pits in the sector addresses. However, said European Patent Application deals with the problem that at 124~6;59 PHN. 11 261 5 the location of the sector address a satisfactory tracking by means of differential method is not possible if the pits of the sector addresses have a depth of ~/4, which corresponds to a phase depth of 18~ for pits having straight walls.
Here, ~is the wavelength of the radiation beam used for reading the addresses and recording the user information. In order to solve this problem it is proposed to give the pits of the sector addresses the same depth as the servo grooves, i.e. the depth of the order of an odd multiple of ~/8, which corresponds to a phase depth of approximately 90 for pits having straight walls. In this record-carrier body the phase depths of the pits and the grooves therefore are not different as in the record carrier body in accordance with the present invention. Moreover, and which is even more important, the ratio between the widths of the servo-track portions and the sector-address areas in the record carrier body in accordance with European Patent Application No.
0,100,995 differs from that in the record-carrier body proposed in the present Application.
In said U.S. Patent 4,587,648 the widths are expressed as the half-intensity width W0 of the scanning spot. The servo grooves have a width of Wo/2 and the pits of the sector addresses have a width of Wo/3, so that the width of the servo grooves is approximately 1.5 times the width of the pits. In a record carier body in accordance with a preferred embodiment of the invention, which is intended to be scanned by means of a radiation spot whose half-intensity width is approximately 800 nm, the width of the servo-track portions is approximatelky 1200 nm, or 3/2.W~, and that of the pits is approximately 600 nm, or 3/4.W~. Further, European Patent Application No. 0,100,995 does not mention anything about the relation between the maximum track width and the track period.
In accordance with a second aspect of the invention ~24!~6S9 PHN 11.261 6 20.6.1985 two radiation spot 9 ~ for recording the servo-track area~ and the sector addresses respectively~ are utilized in order to increase the amplitude of the ~ignal obtained during the subsequent read-out of the information recorded by the user. In accordance with this aspect a record carrier in accordance with the inventiDn i~ characterized in that the servo-track portions constitute continuous tracks and the sector addresses are situated between servo tracks which are ~ituated ad~acent each other in a direc-tion transverse to the track direction.
In this record carrier body a user does not recordthe information in the servo-track portions, as was custo-mary until now, but in the lands between the servo tracks, i.e. on flat parts of the recording lay~r. As a result of this~ the information areas, which comprice mel-ted-away portions of the recording layer, can be detected better than when the~e areas are situated in the servo grooves.
The invention further relates to apparatus for forming a structure of sector addresses and servo-track areas on a photo-sensitive layer of a master disc. This apparatus, which comprises a radiation-source system for producing two radiation beams, a separate intensity modula-tor for each of the beams, and an objective system for focussing the beams to form two radiation spots of different dimensions, is characterized in that the smaller radiation spot is employed for recording the sector addresses and the larger radiation spot for recording the servo-track portions.
It is to be noted that it is known from United States Patent Specification no. 4~027,330 to employ two radiation spots for simultaneously recording information areas and a servo track. In accordance with this United States Patent Specification, however, the wider radiation spot is employed for recording broader information areas and the narrower radiation spot for recording a narrow ~ervo track. The information areas have the form of locally wide-ned portions of the qervo track and are distributed over the lZ ~659 PHN 11,261 7 20.6.1985 entire length of the servo track and hence do not constitute ~ector-address areas.
The apparatuR in accordance with the invention may be characterized further in that, viewed in a direction tran~ver~e to the longitudinal direction ofthe servo-track portions to be recorded, the two radiation spot~
have the same position.
However, preferably, the apparatu~ i~ characterzed further in that, viewed in a direction transverse to the longitudinal direction of the ~ervo-track portions to be recorded, the two radiation ~pots are shifted relative to one another.
The sector addresses are then recorded between the turns of the servo track. The user information is subse-quently also recorded in these lands~ which enables theinformation areas to be read more effectively by means of the integral read method.
For reading the sector addresses and recording information in a record carrier body having continous servo tracks and sector addresses situated between these tracks, a user mu~t employ a write-read apparatus modified in accordance with the invention, This apparatus, which comprises a radiation-~ource system for producing a single or double write-read beam, an inten~ity modulator arranged in the path of the beam, and an objective system for focussing the beam to form a single or double write/
read spot, is characterized in that there is provided an auxiliary beam for the purpose of tracking, which auxiliary beam is focused by mean~ of the ob~ective system to form an auxiliary radiation spot which, viewed in a direction transver~e to the direction of a servo track, is shifted relative to the single or doublewrite/read spot over the distance equal to half the track period in a direction transverseto the track direction.
After the user ha~ recorded information in the record-carrier body in accordance with the preferred embodiment, a record carrier is obtained which is 12~659 PHN 11.261 8 20.6.1985 characterized by continaus ~ervo tracks between which sector addresses are situated, information areas being recorded between successive sector addresses, viewed in the track direction.
Embodiments of the inYention will now be described in more detail~ by way of example~ with reference to the accompanying drawings. In the drawings :
Fig. 1 is a plan view of a part of a record carrier body in accordance with a first embodiment of the invention, Fig. 2 shows two ad~acent sector addresses of this record carrier body to an enlarged scale, Fig. 3 is a radial sectional view of a part of said record carrier body at a location outside the sector lS addresses, Fig. 4 is a radial sectional view of a part of said record carrier body at the location of the sector addresses, Fig 5 is a tangential sectional view of a part of 9aid record carrier body, Fig~ 6 is a plan view of a part of a record carrier body in accordance with a preferred embodiment of the invention, Fig. 7 is a radial sectional view of a part of said record carrierbody at the location of sector addres~es, Fig. 8 is a tangential sectional view of a part of said record carrier body, Figure 9 shows an apparatus for recording the sector addresses and the servo-track portions, in accordance with a fir~t embodiment of the invention, Fig. 10 shows a part of such an apparatus in accordance with a second embodiment, and Fig. 11 shows a combined write/read apparatus for recording and reading information in a record-carrier body in accordance with the invention.
The record-carrier body 1 as shown in Figure 1 comprises a track 10, for example a spiral track~ of which ~2~6~9 PHN 11.261 9 20.6.19~5 Figure 1 ghows only two of the multitude of turns.
Each turn of the track is divided into a large number of sectors~ for e~ample 64 of 128. Each sector comprise~ a servo-track portion 13~ in which a user can record information, and a sector address 12~ in which inter alia the address of the associated 3ervo-track portion 13 is encoded in digital form in optically readable areas 15 shown in Figure Z. Both these area~ and the servo--track portions 13 can be detected optically, 90 that before a block of information is recorded the desired addres~
can be detected and, both before and during recording, steps can be taken to ensure that a write spot accurately follows the servo-track portions. The record-carrier body 1 has a recording layer in which an optically detectable change isproduced when it is expo2led to radiation of sufficiently high intensity.
The method by which and the a E~aratus by means of which the addresses are read and the servo track portions are followed during the recording of the information by the user and the manner in which the recorded user information can be read fall beyond the scope of the present invention and are therefore not described here.
For these subjects reference is made to United States Patent Specification no. 4,363,116.
Figure 2 shows part of two radially adjacent sectors of the track 10. As is shown in this Figure, the sector addres~es are formed by areas 15 which alternate with intermediate areas 16 in the track direc-tion. Between the consecutive turns of the track 10 lands 14 are situated at the same level as the intermediate areas 16. The servo track portions may comprise ridges situated on the surface of the intermediate areas 16 and the lands 14 or, as is shown in Figure 3, grooves recesYed in this surface. In the latter case the sector addres~ areas comprise pits in said surface, which are deeper than the servo grooves, as can be seen in Figure 4.
It is to be noted that for the sake of clarity the iZ4~ 59 widths of the track 10 and of the lands 14 in Figlre 1 have been exaggerated in conparison with the total surface areas of the record carrier. In reality the record carrier body has a diameter of, for example, approximately 30 cm and the radial period Pr~ i.e. the period of the track structure in the radial direction r, is, for example, 1600 nm. The length of the sec~or addresses has also been exaggerated in comparison with the servo track portions 13. In practioe , the length of the portions 13 is, for example of the order 10 of magnitude of 10 to 100 times the length of the sector addresses 12.
Figure 3 is a radial sectional view of a part of the record carrier ~ody, taken on the line 3-3' in Figure 1, at a location where only servo~track portions 13 are situated. The servo-track portions 13 comprise grooves 15 recessed in the surfaces of the lands 14, which grooves can be followed by means of the differential method.
As set forth in British Patent Specification no. 2,034,097 these grooves have a phase depth of the order of 90.
These grooves are shallow and their walls have a large 20 angle of inclination e1, of the order of 80. The substrate 17 carries a thin recording layer 18. This layer may be a reflecting layer, comprisinq, for example, bismuth or tellurium as its principal element. The track structure is then scanned with a beam which is projected from underneath 25 and which traverses the substrate, as is indicated by the arrow 19. Moreover, a protective coating 20 may be provided on the recording layer 18.
Figure 4 is a radial sectional view taken on the line 4-4' in Figure 1, showing a part of the reoord-30 carrier body at the location where the sector addressesare situated. It has been assumed that at the location where the sectional view has been taken two areas 15 are situated adjacent each other in the radial direction.
As will become apparent from a comparison with Figure 3, 35 these areas are deeper than the ser~ trackportions, whilst the angle of inclination ~2 is, for example, of the order of 30 to 60.
,,, i2~9659 Fig. 5 is a tangential sectional view of a part of the record-carrier bcdy, taken on the line 5-5' in Figure 1. As Figure 5 shcws, each sector address comprises an address portion 12a an~ a synchronizing portion 12b, which each comprise a plurality of pits 15 of uniform dimensions, recessed in the substrate. The sequence of pits in the por ion 12a represents the a~dress information.
The pits in the portion 12b have a fixed spatial frequency and upon read-out they produce a clock siqnal for 10 controlling, for example, the clock frequency of a signal source which serves for modulating the amplitude of the write beam with which the user records the information.
By means of a write beam whose intensity is modulated in conformity with the user information to be recorded, for 15 example, pits 22 can be melted in the recording layer at the location of the track portions 13, so that information areas are formed which have a different reflection coe fficient than the surrcunding areas. After the information has been recorded the user has a record carrier in which the servo-20 track portions 13 and the sector addresses 12 constitute aphase structure, whilst the user information has been recorded in the form of, for example, an amplitude structure.
In accordance with the invention, as will be apparent fram Fig~re 1 and a comparison of Figures 3 and 4, 25 the maximum width Wmax 1 of the servo track portions is at least twice the maximum wldth Wmax 2 of the sector-address areas and WmaX1 is larger than half the track period in the radial direction (Pr). In a record carrier for which Pr =
1600 nm and which is intended to be scanned with a 30 radiation spot whose half-intensity value is approximately 800nm, Wmax 1 is approximately 1200 nm and Wmax 2 is approximately 600 nm. The larger width of the servo~track portions ensures that the differential tracking signal has a better signal amplitude than the tracking si~nal 35 obkained from record-carrier bodies Xncwn until ncw, in which the maximum track width is equal to the maximum width of the sector address areas and is, for example, 600 nm.
i24~659 An important advantage is, moreover, that for the specified width of the servo track portions 13 the informa-tion æeas 22 recorded in these portions ky the user can ke read ~etter by means of the integral method than such track s portions 13 having a smaller width. The last-mentioned effect can be explained from the fact that the information areas 22, which differ from their surrounding æea in that they have a different coefficient of reflection, can be detected better when the groove portions 13 æe wider and 10 kear greater resemblance to the flat portions of the recording layer.
The optim~m value of the maximum track width for differential tracking and for integral reading from the sector-address areas provided ky the invention, is the 15 result of inventive use of insights oktained ky vectorial diffraction co~putations. These show that as the servor track portion kecomes wider the amplitudes of the second and higher even diffraction orders decrease and, if the track depth rem2ins the same, the ~.~litude of a first-order suk 20 keam increases as a result of the larger volume of the servo groove or ridge, and that as the maximum track width more closely approximates to the radial period of the track structure the phase depth will come closer to the optimum value of 90, even for larger depths of the servo track.
2s It has keen found that a specific value for the maxim~m track width can ke specified above which the amplitude of the differential tracking signal h ædly increases. For a record carrier kody which has a period Pr f the order of 1600 nm and which is scanned with a radiation spot whose 30 half-intensity value is approximately 800 nm, said value is approximately 1200 nm.
The vectorial diffraction theory teaches that the differential tracking signal is ideal for an effective track width e~ual to approximately half the radial track period.
35 For V-shaped servo grooves this means that the maximum groove width is sukstantially equal to the track period, so that the grooves would adjoin each other. From the point of view of manufacturing technology this is i2~ ;5g PHN 11.261 13 20.6.1985 undesirable. However~ it is also found that for de~iations of the order of 25~ from the ideal track width a ~ery acceptable tracking signal can be obtained.
Therefore~ for practical versions of the record carrier body in accordance with the invention the optimum value for the maximum width of the servo-track portions i9 of the order of 75~ of the radial track period~ Deviations of the order of 20~ from this optimum value are permissible.
Figure 6 shows a record carrier body in accordance with a preferred embodiment of the invention. In this embodiment the servo-track portions ad~oin each other in a tangent~l direction and constitute a continous spiral track or continuous concentric tracks 13. The sector addresses are now situated between the turn~ of the servo track 13.
The optimum value for the maximum width of the servo track 13 is again of the order of 7g~ of the radial period Pr, and the maximum track width is again at least twice the maximum width of the sector-address areas.
Figure 7 is a radial sectional view of a part of this record-carrier body~ taken on the line 7-7' in Figure 6 at the location where the sector addresses are situated.
It is assumed that at the location where this sectional view is taken two areas 15 ad~oin each other in a radial direction. After the description of the first embodiment with reference to the Figures 3 and 4~ Fig. 7 is self-explanatory. Figure 8 is a tangential sectional view of a part of the record-carrier body, taken on the line 8-8' in Figure 6. This Figure also requires no further 3~ explanation.
In the record-carrier body shown in Figure 6 the information areas 22 are recorded by the user ~n the lands between two ~ero-track portions 13 and between two ~ector addresse~ 12. Since the surface for recording the information areas is now entirely flat~ these areas can be read even better by means of the integral method than in the case where the informatiQn areas are recorded in lZ~3659 the wide servo track portions of the record carrier body 1 shown in Figure 1, It is to be noted that the recording of the user-information between the servD grooves or ridges need not be combined with a wider servo groove, but may also be applied to a record-carrier body with a narrcwer servo groove. Recording the information areas between the servo grooves or ridges then also has the advantage that these areas can be read more effectively.
Figure 9 shows the basic diagram of an apparatus by means of which the sector addresses and the servo-track portions on a master disc can be produced. In this Figure the reference numeral 30 denotes the substrate of the master disc, for example a glass substrate. This substrate carries a photo-15 sensitive layer 31, whose thickness has been selected in such a way that the sector-aadress areas, formed after the development of the photo-sensitive layer, have a depth or height which is adapted to the wavelenqth of the beam with which the record-carrier body is to be scanned in order 20 to obtain the correct phase depth. A radiation-source system 33 may comprise one laser or two separate lasers 34 and 35, for example ægon-ion lasers. This system produces tw~ radiation beams bl and b2, of which b1 serves for re-cording the sector addresses and b2 for recording the servc-25 track portions. The narrow beams are widened, for exampleby means of telesco~es comprising lenses 36, 37 and 39, 40 respectively, the beam bl being wiAened more than the beam b2.
Thus, the beam bl is given such a width that it fills a substantial part of the entrance pupil of the objective 30 systems 45. After havin~ traversed its telescope the beam b2 is coupled into the path of the beam bl by the mirror 42 and a beam splitter, for example in the form of a beam-splitting mirror 43. A mirror 44 reflects the two beams to the objective system 45, which focusses each of the beams to 35 form radiation spits V1 and V2, respectively. Since the beam blfills a substantial part of the pupil of the objective system, this beam is focussed to a minimal diffraction-iZ4~659 limited radiation spot. The beam b2, which fills a small part of the pupil, is focussed to form a 'arger radiation spot V2.
By rotating the disc about the axis 32 the radiation s spots V1 and V2 will describe one turn on the disc. For recording a spiral track or a plurality of concentric tracks the radiation spots and the disc should be moved in a radial direction relative to each other either with a constant velocity or stepwise. For this purpose, the mirror 10 44 and the objective system 45 may be accommodated in a housing which is moved in the direction inaicated by the arrow 46.
Mbdulators 47 and 49, for example acousto-optical modulators, are arranged in the radiation paths of the beam 15 b1and the beam b2, respectively, to switch the intensity of the relevant beam in conformity with the signal applied to the terminals 48, 48' and 50, 50', respectively. When the sector addresses are recorded the modulator 47 is switched between a high level and a zero level at a high 20 frequency. In the present apparatus the modulator 49 is then set to the zero level. Durin~ the recording of the servo-track portions the modulator 47 is set to the zero level and the modulator 49 cperates continuously at an intermediate level.
2s The exposure locally increases the solubility of the photo-sensitive layer. The desired relief pattern is obtained by a selective removal of the exposed photo-sensitive material in a development process. The depth and the width of the servo groove are determined by the 30 intensity of the beam b2 and the width of the radiation spot V2, respectively. After the master disc has been developed it may be coated with, for example, a silver layer.
Subsequently, this disc may be used in known manner for the manufactNre of matrices, which are employed for the 35 manufacture of a large number of replicas.
If the chief rays of the beams b1 and b2 are situated in the same X-Y plane, the radiation spots Vl and V2 are superimposed, as sho~n in the inset in the right-~z~s~
PHN 11.261 16 ZO.6.1985 hand part of Figure 9, assuming that the mirrors42 and 43 aro disposed at angles of 45 to said chief rays. Alternatively~ the radiation spots may be shifted in the tangential direction of the disc, i.e. in the Y-direction in Figure 9, in such a way that the radiation spot V1 i9 situated in front. For this purpose the radiation paths of the beams b1 and b2 should be shifted slightly relative to each other in the Y-direction.
For recording continous servo tracks and sector addresses between the turns of the servo tracks it is in principle possible to use an arrangement sim~lar to that shown in Figure 9, in which the modulator 49 is always at the intermediate level and the modulator 47 i9 switched between the high level and the zero level with a high frequency when the sector addresses are being recorded.
The radial shift of the radiation spots V1 and V2 relative to each other can be obtained, for example, by positioning the mirror 42 at an angle which differs slightly from 45 relative to the chief ray of the beam b2, as is shown in Figure 10. This Figure shows only that part of the radiation path where the beams are given different directions, i.e. the part beginning at the mirror 42.
Figures 9 and 10 show the basic diagram of the apparatus for recording the sector addresses and the servo-track portions, in which apparatus a number of variants are possible. For example, the radiation-source system may comprise only one laser followed by a beam splitter. In order to minimize the 109s of intensity this beam splitter and the beam splitter 43 are preferably polarisation-dependent beam splitters and the single radiation source, or the double radiation source 34~ 35, should be capable of producing two beams which are polarised perpendicularily to each other. It is also possible to employ wavelength-selective beam splitters in con~unction with a single ordouble radiation source, emitting two different wavelengths.
A shift of the radiation spots V1 and V2 in a radial direction~ the X-direction in Figure 9~ can also be 12'~!-3659 obtained ky an optical wedge in the p~th of the beam b2, the mirror 42 extending parallel to the beam-splitting mirror 43.
The user of the record-carrier body should have a ccmbined recording/read apparatus at his disposal for recor-ding information and reading this information, and for reading the sector addresses both during recording and during infor-mation reading. Such combined apparatus are known, for example fram United States Patent Spscification no. 4,363,116 and 10 British Patent Specification no. 2,097,150. The known app æatus æe suitable for use in conjunction with a record-c ærier kody in which the sector addresses occupv the same radial positions as the associated serv~-track portions. For a record-carrier body in which the servo~track portions constitute continuous tracks lS and the sector addresses æ e situated between the turns of the servo track, the tracking systemin the known write/read apparatus may be mcdified in such a way that the scanning spot is held at a constant distance from the serv~ track in a way similæ to that described in British Patent Specification 20 2,013,489 for a record carrier with deep and shallcw tracks.
Another possibility is to provide the known write/read apparatus with means for the formation of an additional radiation spot for the purpose of tracking.
Figure 11 shows an example of such an appæ atus. This 2s Figure only shcws the elements of the tracking system. The ele-ment 60 is a radiation source, for example a diode laser, which produces a beam b3. The lenses 61 and 62 constitute a beamr widening telescope which ensures that the beam b3 fills the pupil of theobjective system 67 correctly. Instead of the telescope a 30 lens may be used, which is æranged between the mirror 65 and the objective system 67. The beam reaches this objective system after reflections from the mirror 63, the beamrsplitting mirror 64 and the mirror 65. The objective systemfocusses the beam b3 to form a diffraction-limited radiation spot V3 on the recording layer 18 35 of the record-cærier body 1. This body can be rotated abcut an axis 68, and the mirror 65 and the objective system 67 can be moved together in a radial direction relative to the record-carrier bo~y, the X-direction in Fig~re 11, as indicated by the mirror 75.
124~6S~
The mirror 63 and the beam-splitting mirror 65 serve to couple the auxiliary beam b3 into the mainradiation path of the apparatus, so that all the beams pass through the same ob-jective system. me main radiation path is represented schema-5 tically by a broiad bea~ bo 1 (bo 2) indicated by double arrcws.The block 69 together with the mirror 65 and the objective system 67 constitute the known part of the apparatus. As is descriked in United States Patent Specification no. 4,363,116, it is possible to use only one radiation spot koth for recording and reading.
10 In that case the block 69 co~prises one radiation source, for example a diode laser, a beam~widening and collimating lens system, a modulator, a radiation-sensitive detection syste, and a beam splitter for diverting the radiation which has bPen re-flected by the record carrier body to the detection system which 15 supplies the address signals and the information signals.
Another version of the block 69 produces two radiation beams bo 1 and bo 2 which are focussed by the objective system to form two radiation spots V1 and V2 which are shifted relative to each other in the tangential 20 direction of the record-carrier body, i.e. in the Y-direction in Figure 11. The radiation spots v1, V2 and V3 have the same dimensions. In the present example the block 69 comprises, for example, two diode lasers, a beam splitter for re~ombining the two laser beams after o,ne of 25 them has passed through a modulator, a second beam splitter for diverting the beams reflected by the record-carrier body, a third beam splitter fo,r separating the two beams, and a separate detection system for each of the beams. The beam bo 1~ which forms the radiation spot V1, serves 30 for reading the clock signals and the addresses and for recording the information, and the beam bo 2' which forms the radiation spot V2, is employed fo,r reading the information. For further details about a block 69 which is capable of producing one or two radiation beams reference 35 is made to the United States Patent Specification no.
4,363,116 and British Patent Specification no. 2,097,150, respectively.
i2~96S9 The auxiliary beam b3 is reflected ~y the record-c ærier body and returns along itself until it reaches a beam splitter 70. This beam splitter reflects a part of the beam b3 to a radiation-sensitive detection system ccmprising 5 tw~ detectors 71 and 72. The output signals of these detectors æe applied to a differential amplifier 73. The output signal Sr of this amplifier contains information about the magnitude and the direction of a deviation between the centre of the radiation spot V3 and the 10 central axis of the serv~ track. This signal is employed for correcting the radial position of the radiation spot V3 and those of the radiation spots V1 and V2, for example by piv~ting the mirror 65 in the direction indicated by the arrow 66 by means of an actuator 74 to which the 15 signal Sr is applied.
3~
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A record-carrier body in which a user can record information by means of optical radiation, which record-carrier body comprises a substrate and a recording layer on said substrate and which has been provided with a pre-formed and optically detectable relief structure of servo track portions and sector addresses in which address information about associated recordable portions of the record-carrier body is contained in the form of optically detectable areas which alternate with intermediate areas, which areas in the sector addresses have another phase depth than the servo-track portions, characterized in that the maximum width of the servo-track portions is at least 60% of the track period, transverse to the track direction, and is at least of the order of twice the maximum width of the sector address areas.
2. A record-carrier body, in which a user can record information by means of optical radiation, which record carrier body comprises a substrate and a recording layer on said substrate and which has been provided with a preformed and optically detectable relief structure of servo-track portions and sector addresses in which addresss information about associated recordable portions of the record-carrier body is contained in the form of optically detectable areas which alternate with intermediate areas, which areas in the sector addresses have another phase depth than the servo-track portions, characterized in that the servo-track portions constitute continuous tracks and the sector addresses are situated between servo tracks which are situated adjacent each other in a direction transverse to the track direction.
3. An apparatus for forming a structure similar to the structure of servo-track portions and sector addresses of the record-carrier body as claimed in Claim 1 or 2, comprising a radiationsource system for producing two radiation beams, a separate intensity modulator for each of the beams, and an objective system for focussing the beams to form two radiation spots of different dimensions, characterized in that the smaller radiation spot is employed for recording the sector addresses and the larger radiation spot for recording the servo-track portions.
4. An apparatus as claimed in Claim 3, characterized in that the two radiation spots have the same position viewed in a direction transverse to the longitudinal direction of the servo-track portions to be recorded.
5. An apparatus as claimed in Claim 3, characterized in that the two radiation spots are shifted relative to each other viewed in a direction transverse to the longitudinal direction of the servo-track portions to be recorded.
6. An apparatus for recording and reading information in a record-carrier body as claimed in Claim 2, which apparatus comprises a radiation-source system for producing a single or double write/read beam, an intensity modulator arranged in the path of the beam, and an objective system for focussing the beam to form a single or double write/read spot, characterized in that there is provided an auxiliary beam for the purpose of tracking, which auxiliary beam is focussed by means of the objective system to form an auxiliary radiation spot which, viewed in a direction transverse to the direction of a servo track, is shifted relative to the single or double write/read spot over a distance equal to half the track period in a direction transverse to the track direction.
7. A record carrier comprising a record-carrier body as claimed in Claim 2, in which information has been recorded, characterized by continuous servo tracks between which sector addresses are situated, information areasbeing recorded between successive sector addresses, viewed in the track direction.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8500153A NL8500153A (en) | 1985-01-22 | 1985-01-22 | REGISTRATION CARRIER INCLUDING A RELIEF STRUCTURE OF OPTICALLY DETECTABLE SERVOSCORE PARTS AND SECTOR ADDRESSES AND APPARATUS FOR APPLYING THIS STRUCTURE. |
| NL8500153 | 1985-01-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1249659A true CA1249659A (en) | 1989-01-31 |
Family
ID=19845400
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000499736A Expired CA1249659A (en) | 1985-01-22 | 1986-01-16 | Optical disc having servo-track portions and sector addresses and apparatus |
Country Status (8)
| Country | Link |
|---|---|
| US (2) | US4893298A (en) |
| EP (1) | EP0189948B1 (en) |
| JP (1) | JP2603612B2 (en) |
| AU (1) | AU584662B2 (en) |
| CA (1) | CA1249659A (en) |
| DE (1) | DE3670168D1 (en) |
| HK (1) | HK91391A (en) |
| NL (1) | NL8500153A (en) |
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| NL7809227A (en) * | 1978-09-11 | 1980-03-13 | Philips Nv | RECORD CARRIER WITH AN OPTICALLY READABLE, RADIATION-REFLECTING INFORMATION STRUCTURE. |
| NL7810463A (en) * | 1978-10-19 | 1980-04-22 | Philips Nv | REGISTRATION HOLDER IN WHICH INFORMATION IS PRESENTED IN AN OPTICALLY READABLE INFORMATION STRUCTURE. |
| CA1165871A (en) * | 1978-11-08 | 1984-04-17 | Kornelis Bulthuis | Optically inscribable record carrier |
| NL7902363A (en) * | 1979-03-27 | 1980-09-30 | Philips Nv | RECORD CARRIER WITH AN OPTICALLY READABLE INFORMASTRUCTURE. |
| NL7906576A (en) * | 1979-09-03 | 1981-03-05 | Philips Nv | REGISTRATION HOLDER IN WHICH INFORMATION HAS BEEN INCLUDED IN AN OPTICALLY READABLE INFORMATION STRUCTURE AND READING DEVICE THEREFOR. |
| NL8000121A (en) * | 1980-01-09 | 1981-08-03 | Philips Nv | DISC-SHAPED, OPTICALLY READABLE RECORD CARRIER AS A STORAGE MEDIUM FOR DATA INFORMATION, DEVICE FOR MANUFACTURING SUCH RECORD CARRIER, DEVICE FOR RECORDING DATA INFORMATION RECORDER AND RECORD. |
| NL8000123A (en) * | 1980-01-09 | 1981-08-03 | Philips Nv | DEVICE FOR WRITING DIGITAL INFORMATION IN A DISC-SHAPED OPTICALLY READABLE RECORD CARRIER. |
| FR2490858B1 (en) * | 1980-09-25 | 1986-04-04 | Rca Corp | OPTICAL RECORDING MEDIUM WITH VARIABLE SENSITIVITY AND DISC CONTAINING INFORMATION, MADE BY USING SUCH MEDIUM |
| JPS57105828A (en) * | 1980-12-19 | 1982-07-01 | Matsushita Electric Ind Co Ltd | Optical disk recording and reproducing system |
| NL8100098A (en) * | 1981-01-12 | 1982-08-02 | Philips Nv | RECORD CARRIER WITH OPTICALLY READABLE INFORMATION STRUCTURE. |
| US4359750A (en) * | 1981-04-30 | 1982-11-16 | Eastman Kodak Company | Optical disc structure |
| US4385372A (en) * | 1981-05-01 | 1983-05-24 | Drexler Technology Corporation | Reflective optical data storage and laser recording media having grooved dielectric encoded prerecorded information |
| JPS5823333A (en) * | 1981-07-31 | 1983-02-12 | Sharp Corp | Optical disc |
| JPS5841446A (en) * | 1981-09-04 | 1983-03-10 | Hitachi Ltd | Optical information tracking system |
| US4494226A (en) * | 1981-10-15 | 1985-01-15 | Burroughs Corporation | Three beam optical memory system |
| JPS58150137A (en) * | 1982-03-02 | 1983-09-06 | Matsushita Electric Ind Co Ltd | Optical information recording and reproducing device |
| JPS58155528A (en) * | 1982-03-10 | 1983-09-16 | Matsushita Electric Ind Co Ltd | Optical disc recording and reproducing system, optical disc and its manufacture |
| FR2523349A1 (en) * | 1982-03-12 | 1983-09-16 | Thomson Csf | METHOD AND OPTICAL DEVICE FOR GENERATING POSITION-ASSISTING SIGNALS OF A TASK OF EXPLORING THE TRACKS OF AN INFORMATION MEDIUM |
| JPS5911551A (en) * | 1982-07-12 | 1984-01-21 | Toshiba Corp | Optical information storage medium |
| EP0100995A3 (en) * | 1982-08-10 | 1985-10-16 | Kabushiki Kaisha Toshiba | Optical disk |
| JPS5940339A (en) * | 1982-08-31 | 1984-03-06 | Konishiroku Photo Ind Co Ltd | Information recording medium |
| JPS5965951A (en) * | 1982-10-08 | 1984-04-14 | Toshiba Corp | Original disk for information storage medium |
| JPS59101043A (en) * | 1982-11-30 | 1984-06-11 | Matsushita Electric Ind Co Ltd | Carrier for recording and reproducing information |
| JPS59177744A (en) * | 1983-03-28 | 1984-10-08 | Matsushita Electric Ind Co Ltd | Recording and reproducing disc carrier |
| JPS59207039A (en) * | 1983-05-07 | 1984-11-24 | Kyodo Printing Co Ltd | Optical recording card |
| JPS60132616U (en) * | 1984-02-13 | 1985-09-04 | パイオニア株式会社 | recording device |
| JPS60197953A (en) * | 1984-03-21 | 1985-10-07 | Hitachi Ltd | Information recording device |
| JPS60236137A (en) * | 1984-05-08 | 1985-11-22 | Nippon Kogaku Kk <Nikon> | Simultaneously erasing-recording type photomagnetic recording system and recording device and medium used for this system |
-
1985
- 1985-01-22 NL NL8500153A patent/NL8500153A/en not_active Application Discontinuation
- 1985-05-17 US US06/735,005 patent/US4893298A/en not_active Expired - Lifetime
-
1986
- 1986-01-09 EP EP86200024A patent/EP0189948B1/en not_active Expired
- 1986-01-09 DE DE8686200024T patent/DE3670168D1/en not_active Expired - Lifetime
- 1986-01-16 CA CA000499736A patent/CA1249659A/en not_active Expired
- 1986-01-20 JP JP61008169A patent/JP2603612B2/en not_active Expired - Lifetime
- 1986-01-20 AU AU52484/86A patent/AU584662B2/en not_active Expired
-
1989
- 1989-09-21 US US07/410,691 patent/US4959822A/en not_active Expired - Lifetime
-
1991
- 1991-11-14 HK HK913/91A patent/HK91391A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| NL8500153A (en) | 1986-08-18 |
| EP0189948A1 (en) | 1986-08-06 |
| US4893298A (en) | 1990-01-09 |
| US4959822A (en) | 1990-09-25 |
| AU5248486A (en) | 1986-07-31 |
| JPS61170930A (en) | 1986-08-01 |
| HK91391A (en) | 1991-11-22 |
| JP2603612B2 (en) | 1997-04-23 |
| AU584662B2 (en) | 1989-06-01 |
| EP0189948B1 (en) | 1990-04-04 |
| DE3670168D1 (en) | 1990-05-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |